1. Field of the Invention
The invention relates to an arrangement for heating a motor vehicle interior, especially a truck driver""s compartment, a bus interior or the passenger compartment of a passenger car, with a ventilation means for taking in fresh air via a fresh air intake area and discharging air into the interior, with a heating device for heating of air, and with a warm air line for routing air heated by the heating device into the ventilation means.
2. Description of Related Art
In conventional arrangements of the type to which the invention is directed, the heating device with its warm air line is directly connected to the ventilation means, i.e., the air supplied by the heating device comes into direct contact with the material comprising the individual parts of the ventilation means, so that heatproof material must be used because the warm air supplied by the heating device typically has a temperature between 120xc2x0 and 130xc2x0 C. Nevertheless, there is the danger that the exposed components, typically plastic parts of the ventilation means, can burst or melt due to such a high thermal load. This applies fundamentally also to a frozen windshield which can break due to the high temperature difference between the heating air and the outside air temperature. These problems are, in any case, mitigated by the corresponding addition of fresh air. However, the disadvantage is that in such a known arrangement, as a result of the necessity of having to use heatproof material, the production costs of the arrangement are relatively high. For this arrangement, a heating device is needed which can make available a relatively high volumetric flow in order to be able to overcome the resistances within the ventilation means. This results in high power consumption of the heating device and a high noise level due to flow noise in the ventilation means.
Published German Patent Application DE 196 50 941 A1 discloses a heating and air conditioning device for motor vehicles in which the air emerging from the warm air line is routed into the pressure-side of the fan mixing or distribution space.
In view of this prior art, it is an object of this invention to devise an arrangement of the initially mentioned type which can be economically produced and can be economically operated in the area of the ventilation means, and which offers a high level of comfort as a result of the low noise level.
This object is achieved by the warm air line being routed into the fresh air intake area such that the heated air emerging from the warm air line is taken in jointly with the fresh air into the ventilation means
Instead of indirect delivery of heating air into the ventilation means, the invention takes a completely novel approach by avoiding exposure of the components of the ventilation means to the hot air which is delivered to the ventilation by means of the fresh air taken in. In this way, on the one hand, this results in that by mixing the warm air which is made available by the heating device with cold fresh air its temperature is lowered to a temperature level which is not harmful to the material of the components of the ventilation means itself, if only heat-resistant and not heatproof material is used for this purpose, i.e., material which is typically heat resistant up to roughly 60xc2x0 C. The cost advantages of using the corresponding plastic material are readily apparent. On the other hand, the approach according to the invention results in warm air being delivered by mixing hot air into the fresh air taken in together with it by the ventilation means, so that the heating device need simply make available a volumetric flow which is sufficient to deliver warm air into the fresh air intake area. By using an air heating device with low volumetric flow, power costs are reduced while the noise level in the ventilation system can be kept moderate.
However, the arrangement according to the invention can, therefore, also be built economically because, in the simplest case, it is sufficient to allow the warm air line to end at the fresh air intake area of the ventilation means, where the warm air flow emerging from the warm air line is taken in by the heating device together with the fresh air.
By using simple means, moreover, it is possible to increase comfort in the heating of the motor vehicle interior by means of the configuration in accordance with the invention by controlling the mixing ratio between the fresh air and warm air in the fresh air intake area. Advantageously, a warm/fresh air mixing means of simple structure is considered which, for example, enables temperature setting for the hot air which has been delivered into the motor vehicle interior by changing the exit cross section of the wanr air line and/or the intake channel for the fresh air. Advantageously, in this respect, the invention calls for the mixing means to comprise a fresh air intake chamber with at least one fresh air intake opening and a warm air intake chamber into which the warm air line discharges and which is connected to the fresh air intake chamber via at least one connection opening with an adjustable opening cross section. The fresh air intake chamber can be produced from economical materials, for example, heat-resistant (but not heatproof) plastic, while the warm air intake chamber is advantageously produced from heatproof plastic material or sheet metal.
In the following, the invention is explained in detail with reference to the accompanying drawings.